Gastric mucus secretion will be studied by perfusing rat stomachs in situ with 2N NaCl followed by Ringers solution. The gastric mucosa will be examined by electron microscopy after various periods of exposure and in particular during recovery from the drastic cell exfoliation caused by the hypertonic saline treatment. In addition treatment with distilled water or physiological saline will be used. Once the pattern of damage by 2N NaCl is established, the protective role of various drugs such as prostoglandins, carbonoxolone, cimetidine and others will be used to see if there is a morphological correlate to the protection provided. Another aspect of the study on mucus secretion will be to localize contractile proteins in the gastric mucous cells by the immunolabeling of antibodies to tubulin, actin, myosin, and alpha actinin. After the light microscopy by fluorescent labeling is established, electron microscopical labeling with ferritin and peroxidase will be undertaken.